Concrete Creations: Making Styrofoam Cavities

In part 5, I said that I would next write about my configurable pillar mold. Wellllllllll, I ran into a few challenges with that one. It’s not quite right yet! So, to keep this series going, I wanted to show you how I am making some interesting water features. But before I could do that, I have to share this as it will be used a lot moving forward.

As I explained in Concrete Creations: A Configurable Mold, when I pour concrete shapes I will often use a Styrofoam block to form the cavity. Cutting Styrofoam cleanly is not easy. I did some looking around in YouTube and found some amazing videos by folks who make parts for model airplanes and rockets using hot wire cutters. Based on a few designs I saw, I made a hot wire cutter with a few modifications of my own. It does indeed cut like a hot knife through butter!

This one will also cut 45 degree angles and should make it through 3 inch thick foam no problem. For now, I am using a 12 Volt 1 Amp power supply and a 15 gauge guitar string for the wire. The wire gets to just over 600 degrees which is needed to cut the Styrofoam. I will soon be switching to a 5 Volt 25 Amp computer power supply and Nichrome wire (Bare Nickel Chromium Resistance Wire) which will give me more consistent heat and somewhere in the neighborhood of 730 degrees.

Introducing – My Styrofoam Hot Wire Cutter. Wait till you see my next concrete pours! I can now get REALLY creative with foam cavities!

Introducing – My Styrofoam Hot Wire Cutter.

Now that’s a straight cut!

Cutting angles by tilting the arm that holds the wire.

What’s this you ask? This will be used for a water feature – which I will show you in the next post in this series very soon. This was my first attempt at a cut. The next ones will be even better as I learned quite a bit doing this one.

Also … as I was looking around for ways to sand foam and especially for ways to fill in little indentations (concrete translates the smallest of indents), I came across an AMAZING article written by David Neat called Shaping Styrofoam. You really need to check out his work!

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Gil Namur

Life As A Human's President (and chief bottle washer!), has been writing music, lyrics and poetry since he was a youngster. Spurred on by his friends and family (his daughter Robin in particular), in January of 2009, Gil ... Read Full Profile